1. Field of the Invention
This invention relates to copper base alloys having particular application as connectors or lead frames in electronics. The alloy of this invention comprises a precipitation hardenable nickel-silicon-tin copper alloy to which iron is added within certain limits. The alloy provides improved resistance to cracking or fracture during localized plastic deformation, a fine grain size and improved resistance to grain growth at elevated temperatures. The alloy also provides an excellent combination of properties including bend formability, high strength, stampability and improved resistance to stress relaxation at elevated temperatures.
2. Description of Related Art
One copper alloy used to manufacture electrical connector or leadframe electronic components is designated by the Copper Development Association (CDA, New York, N.Y.) as copper alloy C70250. Copper alloy C70250 has the nominal composition, by weight, of 2.2%-4.2% nickel, 0.25%-1.2% silicon, 0.05%-0.30% magnesium, 0.2% max iron, 1.0% max zinc, 0.1% max manganese, 0.05% max lead and the balance copper and unavoidable impurities. Further details concerning alloys of this type can be found in U.S. Pat. Nos. 4,594,221 and 4,728,372 to Caron et al. Both of which are incorporated by reference in their entireties herein.
United States patents that disclose copper alloys containing nickel, silicon, tin and iron, include U.S. Pat. Nos. 4,971,758 to Suzuki et al., 5,024,814 to Futatasuka et al. and 5,508,001 to Suzuki et al. All of which are incorporated by reference in their entireties herein. U.S. Pat. No. 5,846,346 discloses a copper alloy containing nickel, silicon, tin and an optional addition of iron.
While copper alloys containing nickel, silicon, tin and iron within certain limits are known, there remains a need for a copper alloy with an improved resistance to cracking or fracture during localized plastic deformation, a fine grain size and improved resistance to grain growth at elevated temperatures while maintaining an excellent combination of properties including bend formability, high strength, stampability and improved resistance to stress relaxation at elevated temperatures.